1. Technical Field
The present invention relates to an emissive device, a process for producing the emissive device, and an electronic apparatus.
2. Related Art
In recent years, demands for flat displays having lower power consumption and less weight have been increasing with diversification and the like of information equipment. Organic electroluminescent (EL) devices having luminescent layers are one known example of the flat displays. Typically, the organic EL devices each have a structure in which the luminescent layer is disposed between an anode and a cathode. To improve hole-injection properties and electron-injection properties, a structure in which a hole-injection layer is disposed between the anode and the luminescent layer and a structure in which an electron-injection layer is disposed between the luminescent layer and the cathode have been developed.
Many materials used for luminescent layers, hole-injection layers, and electron-injection layers of organic EL devices easily react with moisture in the atmosphere and degraded. Degradation of these layers causes the formation of a nonluminous region, which is referred to as “dark spot”, in an organic EL device, thus reducing the lifetime of the luminescent device. Accordingly, an important issue in designing of such organic EL devices is to suppress effects of moisture, oxygen, and the like.
To overcome the problems, a method for preventing water and oxygen to permeate by bonding a seal composed of glass or a metal on the substrate of an organic EL device has been commonly employed. However, trends toward larger screens and reductions in thickness and weight of organic EL devices make it difficult to prevent the permeation of water and oxygen with the bonded seal alone. Furthermore, to sufficiently ensure an area for forming driving elements and leads as screens is increased in size, it is necessary to use a top emission structure in which light emerges from a seal side. To achieve such requirements, a seal structure using a thin film that is transparent, lightweight, and strong is required.
To cope with the increase in the size of the screen and the reductions in thickness and weight of the display, for example, JP-A-9-185994, JP-A-2001-284041, JP-A-2000-223264, and JP-A-2003-17244 each have recently disclosed a thin-film sealing technique in which a transparent thin film composed of a silicon nitride, a silicon oxide, a ceramic material, or the like, the film having satisfactory gas barrier properties, is formed as a gas barrier layer on luminescent elements bay a high-density plasma film-forming method, such as ion plating, electron-cyclotron-resonance (ECR) plasma sputtering, ECR plasma chemical vapor deposition (CVD), surface wave plasma CVD, or ICP-CVD. It is possible to prevent the penetration of water into the luminescent elements by the technique.
However, even when the technique is employed, the penetration of water from the exterior cannot be completely prevented, not resulting in sufficient emission properties or emission lifetime. In particular, the occurrence of the detachment of or a crack in a gas barrier layer at the periphery or bumps due to pixel banks and the like causes the penetration of water therefrom. Thus, an attempt is made to prevent a crack in the gas barrier layer by disposing an organic buffer layer having a substantially flat top face at the lower side of the gas barrier layer.
However, the organic buffer layer is formed under reduced-pressure atmosphere. In particular, since a cathode is formed of a thin film in a top emission structure in order to be transparent, a load on the cathode layer causes detachment or a crack at the periphery or bumps. Thus, target emission properties cannot be disadvantageously provided.